Network Packet Transmission

Introduction

• Demonstration of sending IP packets from Host A to Host B.
• Focus on MAC and IP address configuration in packet transmission.

Packet Transmission Details

Initial Packet Setup

• Source MAC Address: Matches Host A.
• Source IP Address: 9.2 (IP of Host A).
• Destination IP Address: 20.2 (IP of Host B).
• Destination MAC Address: MAC address of San Francisco router (not Host B).
  • Ethernet frame goes from Host A to the router; IP packet goes end-to-end.

Using Ping Utility

• Ping Command: Used to send packets to a specified IP address.
  • Syntax: ping 192.168.20.2
  • Sends an ICMP ECHO request.
• ICMP Protocol: Internet Control Message Protocol.
  • Request: ICMP ECHO.
  • Reply: ICMP ECHO REPLY.

Wireshark Network Protocol Analyzer

• Purpose: Captures and decodes network frames.
• Availability: Free on most operating systems.
  • Recommended for learning about networking.
• Usage: Start running to capture sent/received network packets.

Packet Analysis Using Wireshark

ARP (Address Resolution Protocol)

• Function: Resolves MAC addresses for IP packet delivery.
• ARP Request:
  • Broadcast to find MAC for IP 192.168.9.1.
  • Sender’s IP: 9.2, Target’s IP: 9.1.
• ARP Reply:
  • Provides MAC address from San Francisco router.
  • Sender’s IP: 9.1, Target’s IP: 9.2.
  • Enables Host A to learn router's MAC address.

IP Packet Transmission

• IP Packet: Sent once ARP resolution is complete.
  • Source IP: 9.2, Destination IP: 20.2.
  • Source MAC: Host A’s, Destination MAC: San Francisco router's.
• Intermediate Routing:
  • San Francisco router forwards packet towards its destination.
  • Routers in Denver and New York City also involved.
  • New York City router performs ARP request to forward packet to Host B.

Conclusion

• The process involves multiple network layers and protocols (ARP, ICMP, IP) to ensure successful packet delivery.
• The use of tools like Wireshark can greatly enhance understanding of these processes.